Early Season Tree Pests: Eastern Tent Caterpillars & European Pine Sawfly
by Don Janssen, Extension Educator
Pine Sawfly Larvae
Spring has sprung. As trees leaf out, insect pests cannot be far behind. Two of the early pests include Eastern tent caterpillar and pine sawfly.
Although not in huge numbers this year, the white, tent-like webs of eastern tent caterpillar have been appearing in crabapple, apple, cherry, and plum trees. This insect can be a serious problem since it may consume most or all of the foliage. Trees being defoliated so early in the season may become stressed.
If Eastern tent caterpillar appears on your trees, there are several control options. Perhaps the easiest is to carefully pull out the web and destroy it. Do this on sunny, warm days when the caterpillars are inside the nest. In the evening, mornings and the nights when it is not too cold, they are out feeding.
Another control option would be to apply Bacillus thuringiensis (Dipel, Thuricide, etc.), which is a microbial insecticide that is very specific to caterpillars. Other types of insects, including beneficial insects, would not be harmed.
The second early insect to watch for is the European pine sawfly. If branches on short needled pines such as scotch and mugo pine appear to move when you walk past, itís probably a mass of European pine sawfly larva. They will feed on last year's needles, so will disfigure pines but most likely won't kill them.
Control pine sawfly larva with most general purpose insecticides except Bacillus thuringiensis as soon as they appear. Instead of spraying insecticides, another possible option is to knock the larva off the branches with a stream of water or remove them by hand.
Don't cut off infested branches, as the terminal bud will be removed and new growth will not appear on that branch. Pines should only be pruned by cutting back the new candle growth, which typically appears in June.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office